Discharge tube for keeping voltages constant



Aug., 27, 1940. L. KRS ET AL, 2,22,643

DISCHARGE TUBE FOR KEEPING VOLTAGES CONSTANT Original Filed Aug. 22,1936 Patented Aug. 27, 1940 DISCHARGE TUBE FOR KEEPING VOLTAGES CONSTANTLadislaus Krs, Berlin-Tempelhof, Germany, and Jan Friedrich Toennies,New York, N. Y., assignors to Stabilovolt G. m. b. H., Berlin, Germany,a company Application August 22, 1936, Serial No. 97,332. tgrewed June1, 1939. In Germany August 26,

2 Claims. (Cl. Z50-27.5)

It is known to keep consumers voltages constant by means of non-ohmicconductors, which are preferably connected in parallel with theconsumers terminals. Potentiometer arrangements are also known whichconsist of a plurality of series-connected non-ohmic conductors` Asnon-ohmic conductors, that is, conductors, the potential drop of whichis practically constant independently of the passage of current, it ispreferable to use glow discharge tubes. As is well known in the art, aglow discharge tube vis a tube lled with a rarefied inert gas,electrodes being disposed Vinside the tube in spaced relation to oneanother. The electrodes thus form gaps between which a special dischargecalled glow discharge takes place when the electrodes are connected toan electric current source of suitable voltage. A special feature ofglow discharge tubes is the fact that electric current owing throughsuch a tube does not behave in accordance with Ohms law. Glow dischargetubes are thus non-ohmic resistances and it is a characteristic featurethat their potential output is practically constant, irrespective offluctuations in the in-put current within certain limits. A descriptionof a glow discharge tube is contained for example in U. S. Patent No.

1,973,082 of Sept. 11, 1934, to L. Koros, one of the presentco-inventors. When dimensioning 30 such circuits employing dischargetubes, the starting conditions must be taken into account,

that is, insofar as a load is connected in parallel with the non-ohmicconductor, the voltage condtions must, as is well-known, be so chosenthat,

35 inthis case too, satisfactory starting of the glow discharge in thetube takes place. If such a load is absent, the conditions are simpler,since the static voltage of the current source is then available for thestarting operation. In practice,

40 about 50 volts excess Voltage in comparison with the operatingvoltage required to maintain the glow discharge in the tube is generallynecessary for starting. This fact often leads to inconvenience in thepractical design of the necessary circuit arrangements and the inventionhas for its object to provide an arrangement for which a lower excessstarting voltage is sufcient.

The invention solves the existing problem by 50 incorporating in thedischarge tube'an additional path which supplies electrons or ions tothe'space of the path of the glow discharge to be started. Theconstructional design of this arrangement is preferably realised bygiving the intermediate electrode between the auxiliary path accordingto the invention and the main discharge path a perforated form.

Arrangements for carrying out the invention are shown by way of examplein the accompanying drawing in which Fig. 1 illustrates diagrammaticallyan arrangement in simple form,

Fig. 2 illustrates a more complex arrangement in which several maindischarge paths are lncorporated in a common envelope,

Fig. 3 represents a vertical section through one constructional form ofa glow discharge tube potentiometer device according to the invention,

Fig. 4 represents a plan view of the tube. of Fig. 3, and

Fig. 5 is a circuit diagram of a circuit arrangement embodying the tubeof` Fig. 3, by way of example.

Fig. 1 illustrates the principle of the invention in an arrangementwhich employs only one discharge path for keeping voltages constant. Theinvention, however, can equally be employed in arrangements whereseveral discharge paths cooperate in a manner well-known per se forkeeping voltages constant. Such arrangements are illustrated in Figs. 2to 5.

In the arrangement according to Fig. 1, three electrodes I, 2 and 3 arecontained in a glass envelope K. The main discharge space H is formed bythe` electrodes I and 2. The useful load, which is connected in parallelwith the main discharge space H, is denoted by N. It is onlysymbolically illustrated in the figure. The supply of the feedingvoltage is eiected in Wellknown manner through a resistance W. Thecircuit so far described corresponds to that which 'is well-known. Theelectrode 2 is perforated for the purposes of the present invention, asindicated diagrammatically in the figure. The envelope K contains athird electrode 3, by which a discharge path Z is produced between theelectrodes 2 and 3. The electrode 3 is connected to the positive side ofthe supply voltage through a series resistance V. The starting path Z isnot loaded by a consumer. If the supply voltage is connected to thearrangement, the static voltage exists ai; the electrode 3 and thestarting operation is immediately initiated between the electrodes 2 and3. The static voltage does not exist at the path H, as the usefulresistance N is connected in parallel and a current immediatelycommences to flow through N on insertion, that is, the necessary voltagerequired for starting does not exist at the discharge path H. In

the arrangement according to the invention to 0.2 mA. at an excessvoltage of about 0.2 volt,

that is, only one hundredth of the previous amount. As will be seen fromthis numerical example, the current loss owing to the auxiliary path isinsignificant, but the gain owing to the 'decreased expenditure is veryconsiderable, since,

in the hitherto known arrangements mentioned above, either the glowdischarge path had to be given very ample dimensions or the useful loadrst had to be disconnected by means of :a relay circuit and this usefulload could only be inserted after starting, both constituting measureswhich involved additional material or apparatus, with consequentincreased costs.

As has already been stated, the invention may be, and preferably isapplied to glow'discharge potentiometers with series-connected dischargepaths, which are incorporated in a common envelope. In the arrangementillustrated in Fig. 2, a plurality of main discharge paths is providedin a common envelope, there being allotted to each main discharge pathan auxiliary path, by which electrons or ions are supplied to the maindischarge path. Of course, it is not necessary to allot an auxiliarypath to each of the main discharge paths. The arrangement illustrated inFig. 2 has the advantage that certain starting is obtained. Theelectrodes are constructed in disc form. However, the electrodes mayalso have cylindrical, hemispherical orother shape for the purpose ofincreasing the surface area.

The electrodes by winch the main discharge paths are formed are denotedby the reference numbers I-B in Fig.v 2. The electrodes 1 8 areauxiliary electrodes for producing the auxiliary discharge. Theelectrodes are supported by an insulator system II), Which comprises,for instance, individual rings connected together. In the gure, thesupply leads connected to the main electrodes are led out to the rightand the supply leads connected to the auxiliary electrodes to the left.The supply voltage is connected at the terminals I I and I2. As can beseen from the figure, the electrodes 5, 4 and 2, 3 respectively areelectrically connected together, so that a potentiom.

eter comprising three series-connected` glow discharge paths is formed.The potentiometer thus formed from the main discharge paths is connectedthrough the series resistance I3 to the supply voltages. The threeconsumers voltages are derived at they terminals I4-I`I. The startingelectrodes are connected, for instance, through series resistancesI8-20, to the positive terminal II of the supply voltage. 'I'he wholepotentiometer is surrounded by an envelope 2| (glass, metal or thelike). The supply leads are protected within the envelope by insulatingsleeves 22.

As can be seen from Fig. 2, the electrodes I, 3 and 5 belonging to themain discharge paths have apertures at the centre. However, a pluralityof perforations may also be provided. Only the immediate surroundings ofthe perforation are decisive for the development of the discharge.Therefore, it; is possible to ll the space between the auxiliaryelectrodes and the respective perforated electrodes largely withinsulating material and to allow the discharge to arise only in theimmediate surroundings of the apertures.

It is sometimes important to take care in manufacture that the dischargedoes not arise between the electrodes of the auxiliary ionisationchamber and the agjacent main electrodes (e. g., auxiliary electr de andmain electrode 4) This can be preve `t by making the distance, e. g.,between the auxiliary electrode 9 and the main electrode 4, greater thanthe distance between the electrodes forming a main discharge path, or bycovering the auxiliary electrodes'or main electrodes, or even both, onthe particular sides which come into question with insulating materialor, alternatively, in the case of activated tubes, by not activating theopposite surfaces at which starting is not to take place. Although anydischarge at such surfaces does not in itself prevent the operation ofthe tube, the starting of the discharge in the ionisation pathsthemselves is to be prevented as much as possible from being endangeredon the occurrence of such a discharge. In the arrangement illustrated inFigs. 3 to 5, a potentiometer tube is shown in winch electrons or ionsare supplied to only one of the main discharge paths. It is particularlyadvantageous to employ such a potentiometer tube in circuits which servefor feeding amplifying arrangements. In such arrangements, for example,one discharge path is used for deriving the grid biases and theremaining paths are used for deriving the anode voltages. Itis thenparticularly important to ensure satisfactory starting of the dischargepath from which the grid voltages are derived.

The electrodes are denoted by the reference numbers I to 4, and areconstructed in cap form, that is, the electrodes each consistsubstantially of a cylinder closed at one end. The open ends of theelectrodes are closed by a plate 5 of insulating material. In theinsulating material grooves are provided, in which the caps are seated.'I'he discharge paths are formed in wellknown manner between theelectrodes I, 2; 2, 3 and 3, 4 respectively. In a frequently employedpotentiometer circuit, the electrode 4 is connected to the positive poleof a supply voltage through a suitable series resistance, while theelectrode I is connected to the negative pole of I is circumferentiallyinterrupted and is surrounded at this zone by an electrode 6, which, inturn, is insulated from the electrode I by interposed insulatingmaterial I but is supported by the electrode I. It is not necessary toeffect a circumferential interruption, but it is suicient to provide thecap I at different points with apertures. The ring 6 may be connecter toa supply through the supply lead 8 which (as illustrated) is led out ofthe top of the potentiometer tube, but may be led out at any othersuitable point. The lead 8 is preferably insulated by anAinsulatingsleeve 9.

The circuit connections of the potentiometer tube illustrated in Figs. 3and 4 will be seen from Fig. 5. By means of the electrode I, 6, theauxiliary discharge path is formed, which supplies electrons or ions tothe main discharge path I, 2. The voltage necessary for producing theauxiliary discharge is derived in the same manner as in Fig. l, from thepositive pole of the supply voltage through a series resistance I0. Themode of operation is the same as described above with reference toFig. 1. In the present case, the projection of ions and electrons fromthe auxiliary electrode into the space between the main electrodes,greatly facilitates the electric discharge between the main electrodes.

What we claim. is:

1. A glow discharge potential divider, comprising a container, aplurality of electrodes disposed in said container parallel to oneanother and one behind the other, said electrodes forming a plurality ofseries interconnected glow discharge gaps, a current inlet terminal anda current outlet terminal connected to the rst and last of saidelectrodes, the said last electrode being periorated, an auxiliaryelectrode for emitting electrons to the space of the path of the glowdischarge and being spaced from said perforated electrode and disposedin said container for cooperation with the latter, whereby the startingof the glow discharge in said series interconnected discharge gaps isfacilitated.

2. The device claimed in claim 1, in which the breakdown resistancesbetween the said electrodes forming a plurality of glow discharge gapsand the said auxiliary electrode are of predetermined values in relationto the operating currents, whereby glow discharge is limited to the saidglow dischargel gaps aforementioned, while glow discharge is preventedbetween the said auxiliary electrode and any other electrode, and inwhich the said electrodes are cup-shaped structures nested within eachother, the said perforated electrode being formed by the outer-most cup,and an insulating member surrounding each perforation of said perforatedelectrode being interposed between the latter and the said auxiliaryelectrode.

LADIsLAUs KRs. JAN FRIEDRICH TOENN'IES.

